Inmate John Winfield was put to death in the US state of Missouri. Photo: Reuters

He was the 23rd inmate executed this year in the United States, which allows individual US states to decide if they will use capital punishment, and implement it if they choose it.

On Tuesday and early on Wednesday one execution was carried out in Georgia and another in Missouri.

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Both – also by lethal injection – came after last-minute appeals were rejected by the US Supreme Court.

In the first of them, Marcus Wellons, 58, convicted of the 1989 kidnapping, rape and murder of a 15-year-old girl, was put to death shortly before midnight in the southern state of Georgia, a spokesman for the prison system said.

In the second case, John Winfield, 43, convicted of killing two women, was executed in the central state of Missouri.

The bungled April 29 execution in Oklahoma provoked accusations of torture.

Clayton Lockett, a convicted killer and rapist, was put to death by lethal injection in a process that took 43 minutes, well beyond the usual time of a little more than 10 minutes.

He was seen writhing in pain, bucking off the gurney and mumbling unintelligibly in a spectacle that drew widespread condemnation, even from President Barack Obama.

Mr Obama, who backs the death penalty for heinous crimes, condemned the incident as "deeply troubling".

He ordered Attorney General Eric Holder, who is seeking the death penalty in the Boston Marathon bombings case, to conduct a policy review of how the death penalty is applied in the United States.